Gateway School District communications director Cara Zanella explains what goes into the decision to call a two-hour delay or cancel school on a cold day. They look at factors like road conditions in Monroeville, student safety, daily temperature forecasts, infrastructure, heating and whether school buses will start.

Some parents emailed WTAE.com or posted a question on WTAE's Facebook page, asking why a one- or two-hour delay is necessary on a cold day. Road conditions? Infrastructure? Heating in buildings? Student safety?

"The short answer to that is, yes," Gateway School District communications director Cara Zanella said. "We take everything into consideration when we're looking for a delay."

Zanella told WTAE Channel 4 Action News reporter Sheldon Ingram that each school district has its own parameters to determine closures and delays.

"When it snows outside, it's a different thing. We're looking at the roads, and we can make a determination based on the conditions right at that point," she said. "Weather delays are a whole other situation, with regards to temperature. Temperature delays create a problem because there's no set rule to tell us what's too cold."

In cases where roads are perfectly dry but temperatures are very cold, Zanella said the district first considers the welfare of children -- mainly the ones waiting at school bus stops.

"How's that going to impact the children, as far as standing at the bus stop?" Zanella asked. "Are buses going to be able to kick over and start when we need them to?"

If the temperature starts at dangerously low levels, like the single digits, Gateway checks the weather forecast to see if temperatures are expected to move upward of 15 to 20 degrees. In that case, a delay would be scheduled. But if the forecast calls for brutal temperatures to lock in and not budge, then Gateway would likely cancel classes for that day.

Zanella said their concern is about the potential for hypothermia, and skin exposure for the children who wait at bus stops early in the morning. She said it's a health and safety consideration that influences delays or closures. Issues regarding buildings and transportation are secondary.

"Single-digit temperatures this morning, with even a light wind, takes the wind chill down to 15 to 20 below zero. Pretty quickly, you can start to experience symptoms of frostbite," said Dr. Chadd Nesbit, an emergency medicine doctor at Allegheny General and West Penn hospitals. "Within five to 10 minutes of being outside, certainly a half hour, you can start to do some significant tissue damage to exposed flesh at that point."